Ultralow dark current p‐type strained‐layer InGaAs/InAlAs quantum well infrared photodetector with background limited performance for T≤100 K

An ultralow dark current normal incidence p‐type strained‐layer In0.3Ga0.7Al/In0.52Al0.48As quantum well infrared photodetector (PSL‐QWIP) grown on (100) semi‐insulating InP substrate by molecular beam epitaxy technique for 8–12 μm infrared detection was demonstrated for the first time. This PSL‐QWIP shows background limited performance (BLIP) for T≤100 K, which is the highest BLIP temperature ever reported for a QWIP. Due to a 1.5% lattice mismatch between the substrate and quantum well, a biaxial tensile strain was created in the In0.3Ga0.7As well layers. As a result, the light‐hole state becomes the ground state for the free hole with small effective mass. The dramatic increase of optical absorption can be attributed to the large in‐plane density of states and the small light‐hole effective mass as a result of heavy‐ and light‐hole state inversion. The dark current density and BLIP detectivity for this PSL‐QWIP were found to be 7×10−8 A/cm2 and 5.9×1010 cm−√Hz/W, respectively, at λp=8.1 μm, Vb=2 V, and...